Since 1987, the swine-producing industry has been subjected to a devastating epidemic of an unknown disease, often referred to as "Mystery Swine Disease" [MSD, more recently referred to as "Swine Infertility and Respiratory Syndrome (SIRS)], because researchers have been unable to identify the causative agent. MSD has affected hundreds of thousands of swine throughout North America and Europe. Once one pig is infected with MSD, that one pig can spread the MSD to an entire herd within three to seven days. From 1987 to 1991, the swine industry has lost millions of dollars in revenue as a result of MSD. A recent study estimates that MSD causes a financial loss between $250 and $500 per inventoried sow.
MSD causes multiple symptoms in swine. The first symptom of MSD in a breeding herd of swine is usually anorexia and mild pyrexia. In addition, the herd animals may exhibit bluish discolorations in their skin, especially in their ears, teats, snout, and the frontal portions of their necks and shoulders. The affected skin may become irreparably damaged. However, the most devastating symptom of MSD is the reproductive failure that occurs in a breeding herd of swine. MSD causes sows to bear stillborn piglets; undersized, weak piglets with respiratory distress; or piglets which die before they are weaned. Other reproductive symptoms caused by MSD include early farrowing of piglets, a decrease in conception rates, failure in some sows to cycle, and a reduction in the total number of piglets found in a litter. It has been estimated that the number of pigs lost from reproductive failure is about 10 to 15 percent of the annual production of pigs.
Research has been directed toward isolating the causative agent of MSD. A number of potential bacterial pathogens have been isolated. However, the types of potential bacterial pathogens have varied between swine-producing farms. Viral investigation has included fluorescent antibody examination, electron microscopic investigation, and serology. These methods have failed to locate the causative agent of MSD. As a result, no one has yet developed a vaccine which can be used to treat MSD in the swine population.
Therefore, it is an objective of the invention to provide a vaccine and sera which, when administered to a breeding swine herd, will reduce the presence of MSD in their population. Another object is to provide a method of treating a population of swine with the vaccine to eradicate MSD from the swine population. Yet another object is to provide a method for diagnosis of MSD.